Devices are known in the art to capture images described by contact on a surface. A primary, although by no means exclusive, application for such imaging devices is in the area of fingerprinting, whether for security, forensics or other purposes. Other applications include analysis of surface texture for classification or testing purposes, or recording contact for archival purposes, or possibly mechanical duplication.
All of the foregoing applications involve translating the image described by contact into a reproducible record of the image. For example, in the fingerprint application, a time-honored system is to "ink" the fingers and roll them on a paper or card surface. Of course, without further scanning of the results, such systems lack the capability to generate computer-ready signals representative of the images. Without the storage and analysis capabilities of a computer, cataloging and comparison of such fingerprint images is a time-consuming and unpredictable task.
More recent devices shine light onto the fingerprint via a prism. The reflected image may be captured on photosensitive film, or received onto a photosensitive array. In the latter case, the image may then be pixelated and stored as an analog or digital signal representative of the image. These signals are now available for further processing by computers.
The prior art references cited with this disclosure demonstrate that fingerprinting is a popular application of the "reflected image" technique. The same "reflected image" technique is also known to be used to scan paper or other textile images into scanners and photocopiers.
The disadvantage with all devices employing a "reflected image" technique of recording images is that by definition they need an independent light source and optical structure (such as a prism) to create a reflected image. The same is true of "reflected image" techniques using radiation outside the visible light band of the electromagnetic spectrum. By definition, an independent radiation source and reflective/diffractive structure is still required.
Other current art devices generating images by contact use proximity sensors to detect changes in characteristics such as capacitance or magnetic flux. The disadvantages of these devices are that (1) they can be unreliable, and (2) they can be costly. They are unreliable inasmuch that in detecting variations in, say, capacitance, there is no way to know whether capacitance change is caused by contact or by some other stray source. Further, an expense must be incurred in such devices in creating sensor circuitry having fidelity and resolution comparable to the capability of capturing and resolving reflected radiation such as visible light.
There is therefore a need in the art for a device generating images described by contact, where the contact is the primary source of energy for the image itself. In this way, the extra structure required in "reflected image" techniques would be obviated. Further, it would be highly advantageous if such an inventive device did not rely on proximity sensors to detect the contact. The inventive device would then have increased predictability in performance, without requiring complex sensor circuitry to interpret the contact.